The invention relates to a process for the torsionally resistant connection of a hollow shaft to at least one part arranged on the shaft, in which process the part is fitted with mating play onto the shaft and is fastened in a specific position on the latter by eliminating this play.
It is known to fasten cams, for example, on shafts by shrink-fitting or by expanding the tubular shaft. For shrink-fitting (DE 33 01 749 A), a heated cam can be pushed onto The shaft and shrinks securely on the said shaft by contracting during cooling. A tubular shaft can be expanded by applying appropriately high, fluidic internal pressure to achieve frictionally engaging contact with the bores of cams arranged on the shaft (DE 38 03 687 A).
It has also already been proposed (DE 36 38 310 A) to use a shaft of a cross-sectionally unround outer contour, onto which cams of correspondingly unround outer contour are fastened. The fastening of the cams on the polygonal shaft is Intended to take place by interlocking actions of the polygon shape to be brought about by expanding the polygon faces or by compressing the polygon shoulders when pushing on the cams and the subsequent springing back of the polygonal tube.
Furthermore, it has already been proposed (DE 25 46 802 C) to provide the seating of the cams with an unround design and to deform the wall of the tubular shaft into the unround seatings of the cams by generating high pressure in the space inside the shaft.
It has been found, however, that the frictional engagement which is required for the transmission of the forces occurring during operation of the shaft is not always achieved with the required reliability. The expanding of a tubular shaft by internal pressure requires considerable time to build up the very high necessary, with the result that the cycle time for this method of production, and consequently its costs, are high.
It was therefore the object of the invention to provide a simple and inexpensive possible way of fastening parts such as cams, discs, gear wheels and the Like securely on shafts, in particular such that they are secured against torsion.
The expanding of a hollow shaft by means of a drift moved through the shaft is a deforming technique which is uncomplicated and easy to carry out. The amount by which the hollow shaft has to be expanded in order to accomplish the desired secure seating of the parts is generally small and therefore does not present problems either in terms of working methods or in terms of materials. In extreme cases, the expanding may also be performed in stages, in that a plurality of drifts are moved in succession or a staged drift with increasingly larger expanding diameters is moved through the hollow shaft. With this embodiment, there is the associated advantage that the material can relax after the deforming operation before the next expanding operation follows. In this way, the risk of micro-structural damage can be avoided.
The drift may be pushed through the shaft, but it is preferred for it to be pulled.
The hollow shaft is generally circular in cross section on the inside and outside, as is the bore of a part to be fastened on the shaft. The contours of these parts coming into engagement with one another may, however, also be unround, for example oval or polygonal, and also have the same cross section as one another or a sightly different cross section from one another.
A particularly secure seating of a part to be fastened on the hollow shaft is achieved if the bore of this part has a profiling, for example in the form of a toothing, into which the material displaced during expansion of the hollow shaft flows and thus brings about a keyed connection between the part and the shaft. FIG. 1a is a view of a plurality of drifts which may be successively used in the process.